1. Technical Field
The present invention is related to a metal stripping additive and composition containing the same; more particularly to a gold stripping additive and composition containing the same.
2. Description of Related Art
From ancient times, minerals are closely linked with the development of human society and science. Nowadays, their importance is even more in the electronic industry of modern technology. Various elements of electronic industry, such as a central processing unit, a printed circuit board, a memory, a flip chip, or even a concealed antenna equipped inside the outer shell of a mobile phone, contain metal-plated parts. In fact, those metal-plated parts play important roles in the device. However, minerals resources are not unlimited; therefore, under the sustainable development consideration, how to recycle the metal materials from those metal-plated parts has become a critical task in the industry.
Unlike most of the other metals, gold is an inert metal with highly stable chemical properties, therefore, it is not easy to strip it from waste products and there is only a few recycling methods are available. Aqua Regia method and cyanide method are the two gold-stripping methods used in the field.
Aqua regia is an acid liquid made by mixing concentrated nitric acid and concentrated hydrochloric acid at a volume ratio of 1:3. It is capable of dissolving most of the metal materials including gold. Aqua regia has extreme corrosion; therefore, even if the preparation thereof is easy, it still is not the dominant choice in the field under safety concern. Moreover, except for the metal-plated parts desired to be recycled, the substrate itself or other components of the electronic elements are also valuable. That said, it is not ideal because if aqua regia is used for recycling the metal material from waste electronic elements, the other components of the waste electronic elements will also be destroyed by the extreme corrosion property of aqua regia and fail to be recycled.
Cyanide method is the mostly used gold-stripping method in the field. Although cyanide does not have the disadvantage of harmful corrosion property as aqua regia does, it has high bio-toxicity that causes high risk in operation and storage. In addition, the waste liquid resulting from cyanide method contains a high concentration of cyanide. In order to comply with the environmental safety regulations, the waste liquid has to be diluted for at least 500 fold. This additional processing cost is also a burden for business.
Taiwanese Patent Publication No. 201247941 discloses a novel gold-stripping composition. Its components while operating with electrolysis method effectively strip gold from recycle materials. However, the application of the aforesaid gold-stripping composition is limited as some electronic elements adopt substrates with no conductivity.
In light of the foregoing, a metal-stripping composition being operating-friendly and able to be widely applied is in need in the field.